The High Voltage Electron Microscope Facility is a Biotechnology Resource of the Biotechnology Resources Branch of N.I.H. and is available to bio-medical researchers for ultrastructural studies where use of a high voltage electron microscope can provide new information. Investigations will be directed especially towards analysis of relatively large and complex three-dimensional cell structures either in intact cells or isolated organelles, such as isolated flagella and chromosomes, or in sections up to 1 or 2 microns thick. The possibility for imaging undehydrated biological specimens in a special environmental chamber will be investigated. Freezing and freezing-related procedures will be developed to expand the usefulness of the cold stage. Frozen sections, whole specimens, isolated cell components, and aqueous suspensions will be studied in this manner. Methods of 3-dimensional image reconstruction applicable to thick biological specimens will be further developed. Image intensifier, television viewing, scanning densitometer, and minicomputer are also available to investigators.